import java.util.Scanner;

public class Test {
    public static int fib(int n) {
        if(n == 1 || n == 2) {
            return 1;
        }
        return fib(n-1)+fib(n-2);
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int ret = fib(sc.nextInt());
        System.out.println(ret);
    }
}
